Preparation And Drug Loading Property Of Fluorescent Chitosan Nanoparticles

As a new kind of drug carrier with good biocompatibility, non-toxic side effects, biodegradability and sustained-release, C hitosan(CS) nanoparticles have attracted more and more attention of researchers. Fluorescent carbon quantum dots(CQDs) have been extensively used as fluorescent markers for nanocarriers and tumor cells. In this paper,fluorescence CQDs were synthesized by pyrolysis method, and then chitosan-carbon quantum dots(CS-CQDs) fluorescent nanoparticles were synthesized via one-step ionic gelation technique. 5-fluorouracil(5-Fu) was loaded onto CS-CQDs to obtain 5-Fu-CS-CQDs nanoparticles. The preparation conditions and structural feature of CQDs, CS-CQDs and 5-Fu-CS-CQDs nanoparticles was investigated, and meanwhile the fluorescence properties drug- loading properties and cytotoxicity were studied. Main content as follows:1?In this section,research progress of nanocarriers, CS nanoparticles and CQDs recently were briefly summarized and the significance of this research was suggested.2?The CQDs were synthesized by high temperature pyrolysis method and microwave heating glycerin method, respectively. Both products exhibit strong blue-green fluorescence, when exposed to 365 nm UV light. The CQDs synthesized by high temperature pyrolysis method have a diameter of 5 nm with a UV absorption peak in 330 nm, and their maximum excitation wavelength and maximum emission wavelength are 365 nm and 460 nm, respectively. For another method, the synthesized CQDs have a diameter of 11 nm with a UV absorption peak in 260 nm, and their maximum excitation wavelength and maximum emission wavelength are 310 nm and 456 nm, respectively.Therefore,high temperature pyrolysis method is better than microwave method. The suitable conditions of high temperature pyrolysis to synthesize CQDs with strong luminescence intensity were 180 ?(temperature) and 30 min(reaction time). There are abundant of carboxyl groups on the surface of CQDs obtained, and their fluorescence intensity increased with p H. The CQDs have low cytotoxicity on SMMC-7721 cells at low concentration(< 200 ?g/m L), and thus can be used for cell fluorescence labeling.3?The CS-CQDs fluorescent nanoparticles were synthesized via one-step ionic gelation technique. When the chitosan concentration was 2.5 mg/m L(20 m L), the volume of CQDs aqueous solution was 2 m L, final p H value was 5.0 and reaction time was 2 h, the CS-CQDs fluorescent nanoparticles can be obtained with a small partical size about 290 nm. The nanoparticles have dispersible uniformity and good stability, and the fluorescence intensity of CS-CQDs increases with the volume of CQDs. Moreover, CS-CQDs have low cytotoxicity on SMMC-7721 cells and can be used for fluorescence micro- imaging system.4?The 5-Fu-CS-CQDs fluorescent nanoparticles were also synthesized via one-step ionic gelation technique. The optimum conditions are selected through single factor and an orthogonal experiment as: chitosan concentration(3 mg/m L(20 m L)), 5-Fu concentration(5 mg/m L), CQDs aqueous solution volume(2 m L), final p H value(5.0) and reaction time(2 h). Under the optimum conditions, 5-Fu-CS-CQDs fluorescent nanoparticles with maximum drug loading(about 34.69%) and encapsulation efficiency(about 28.71%) can be obtained. The 5-Fu-CS-CQDs have a particle size range of 200 to 600 nm, and their fluorescence intensity is increased with the volume of CQDs. The cumulative release percent of 5-Fu-CS-CQDs within 48 hours in PBS solution(p H=7.4) was 36.82%, which exhibits obvious sustained-release behavior compared with bulk drug of 5-Fu. In addition, the higher content of 5-Fu, the more obvious the burst effect of 5-Fu-CS-CQDs will be. The cumulative release percent of 5-Fu-CS-CQDs was decreased with the increase of CQDs amount, and increased with the decrease of p H value. The data fitting result showed that the in vitro drug release of 5-Fu-CS-CQDs was fitted to Ritger-Peppas model. MTT results showed that 5-Fu-CS-CQDs have similar cell-killing effect on SMMC-7721 cells compared with bulk drug of 5-Fu, and also can be used for fluorescence micro- imaging system.